1. Field of the Invention
The present invention generally relates to a method for processing a substrate by plasma-assisted process, such as plasma-assisted deposition and plasma-assisted etching, particularly to a method for controlling in-plane uniformity of a substrate subjected to such processing.
2. Description of the Related Art
In a plasma-enhanced atomic layer deposition (PEALD), RF power is an important parameter for controlling the quality of a film depositing by PEALD. In general, high RF power and prolonged duration of plasma exposure contribute to good quality of a film. However, according to the present inventors' experience, when RF power is high, an area of the film near the outer periphery has a thickness greater than that of other areas of the film, i.e., in-plane uniformity of thickness of a film is degraded. Although the reasons for such in-plane unevenness of thickness of a film are unknown, the present inventors expect that unevenness of thickness may be caused by uneven adsorption of a material over a substrate surface due to uneven distributions of plasma and/or uneven activation on the substrate surface, or insufficient purge around the outer periphery of the substrate. Further, in trimming photoresist and carbon film, the etch rate of a film on a substrate is higher near the outer periphery of the substrate than inner areas of the substrate.
The above and any discussion of problems and solutions involved in the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion were known at the time the invention was made.